Sheet feeding mechanisms



Jan. 3, 1956 Q H. T. BACKHOUSE 2,729,448

SHEET FEEDING MECHANISMS Filed Aug. 13, 1952 2 Sheets-Sheet l (r gwzmab 3, 1956 H. T. BACKHOUSE SHEET FEEDING MECHANISMS 2 Sheets-Sheet 2 Filed Aug. 13, 1952 a R m JUL w tinned St P fl fi 2,729,448 SHEET FEEDING MECHANISMS Headley Townsend Backhouse, Nassau, Bahamas Application August 13, 1952, Serial No. 304,102 Claims priority, application GreatBritain August 31, 1951 8 Claims. (Cl. 271-56) The invention relates to sheet feeding mechanisms of the kind which are employed in conjunction with printing and like machines operating on a succession of single sheets of paper, card and the like and in which the sheets are fed by conveyor means to a feed-board from which the sheets are transferred individually to the printing or other machine. Usually the mechanism also effects registration of the position of each sheet on the feed board before it is transferred to the printing machine. 7 It is also usual (but not essential) that such mechanisms form a part of, or are used in conjunction with, machines in which the sheets are, as a preliminary operation, separated from a pile or stack and placed on the conveyor means either as individual sheets or as a streamof partly under-lapping sheets.

It sometimes happens, in mechanisms of the above kind, that sheets which have not been properly separated from one another are fed to the feed-board by the conveyor and that, unless suitable precautions are taken to avoid the eventuality, two or more superposed sheets are transferred to the printingor other machine with undesirable consequential results. Various mechanisms (called two-sheet detectors) have been proposed for detecting the arrival on the feed-board of two or more superposed improperly separated sheets. t

The present invention is concerned with a two-sheet detector in a sheet feeding mechanism of the above kind and which is of the type employing a pair of suction nozzles respectively above and below the sheet about to be transferred from the feed-board and closely adjacent to the surface of the sheet the arrangement being that a single sheet can be drawn, by the suction, against only one of the nozzles whereas two superposed sheets maybe drawn, with a slight separating movementof thesheets, against and thereby seal, the two nozzles respectively and that simultaneous sealing of the two nozzles causes the operation of means forstopping the transfer of the sheets and/or the operation of a warning device.

One construction of a two sheet detector of the above type is described in my British patent specification No. 688,629, dated December 20, 1949.

it is usually desirable that in two-sheet detectors of the above type there shall be valve means controlling the application of suction to the nozzles in such timed relation with the operation of the sheetfeedingmechanism that the suction shall be effectively applied with a high degree of precision in relation to the cycle of the mecha nism. For instance when the mechanism effects registration of the sheets it is usually desirable that the suction be effective immediately after registration has been completed. If the suction is effective before completion of registration then the detector may interfere with the registering operation whereas if it is not effective until later then time is wasted. In other applications proper valve control is desirable to avoid waste of suction. A difficulty which has been found in the valve control means as previously proposed for this purpose is that there has been a time lag between the opening of the valve and the build 2,729,448 Patented Jan.v 3, 1956 up of suction at the nozzle mouths and that the build up has been gradual. This ditficulty, which it is an object of the invention to reduce, has been due to the fact that substantial lengths of suction tube have been employed be tween the valves and the orifices and that the evacuation of such tubes takes time. The use of such tubes has been that there are two suction control valves for the two nozzles respectively, that the two valves are positioned above and below the feed-board respectively and are directly connected to the nozzles to which they are appropriated and that means for operating the valves are provided extending to the valves above and below the feed-board.

Preferably there is also provided, at least for the lower nozzle, an adjustable relief valve in the suction connection to the nozzle, the relief valve controlling a lead to the atmosphere and being positioned either in the connection between the control valve and the nozzle or immediately before the control valve in the supply to the nozzle. The purpose of the relief valve or valves is to enable the degree of suction at the nozzle to be varied, to suit different grades of paper, without appreciably affecting the timing.

Two specific examples of machines embodying the above and other features of the invention will now be described with reference to the drawings which are largely jdiagrammatic and in which:

Figure l is a perspective view, partly broken away, of one machine,

Figure 2 is a plan view of the lower-valve box,

Figure 3 is a section on the line 3-3 in Figure 2;

Figure 4 is a section on the line 4-4 in Figure 2,

Figure 5 is a side view illustrating the operation of the detector, and

Figure 6 is a section through the second example and includes a wiring diagram.

The machine forming the subject of the first example and shown in Figures 1-5 has a feed-board 10 and associated therewith in well known manner there are front lays 11 and side-lays (not shown). The feed-board is supported on frame members 12 at each side of the machine considered in relation to the direction of movement of the sheets over the board. Supported on the underside of the feed-board a short distance behind the front lays and at about the centre of the board, there is a valve box 13. A suction tube 15 is connected to one side of the box and extends through one side frame 12 to a source of suction so as to maintain a constant supply of suction at the box. Extending upwardly from the box 13 and through the feed-board 10 to the upper surface thereof there is a suction nozzle 16, the lower end of the nozzle being connected within the valve box to the suction supply tube 15. There is a piston valve 17 within the box in the connection to the nozzle 16, the valve having a shank or push rod 19 which extends rearwardly from the box and constitutes a follower for a cam 20 on a constantly rotatable cross-shaft 21 mounted in hearings in the two side frames. The arrangement is that rotation of the shaft 21 causes the cam 20jto open the valve 17 (see Figure 3) to connect the nozzle 16 to the suction supply tube 15, immediately after registration of each sheet has been effected. There is also an adjustable relief valve 25 in the box in the connection between the piston control valve 17 and the nozzle orifice 16. Also within the valve box is a piston 30 and cylinder 31 of which the cylinder forms a part of the connection between the piston valve 17 and the orifice 16. The piston and cylinder are arranged so that when suction in the supply line between the piston valve and the orifice builds up as later described, the piston moves in the cylinder, to the left as viewed in Figure 4, and projects a piston rod 32 into the path of a check member (not shown) of the machine thereby to stop the machine. The relief valve 25 comprises a cylindrical socket 35 in the top surface of the valve box 13, two passageways 36 leading from the base of the socket to the suction cylinder and an annulus 37 within the socket, the annulus having holes 38 which may be moved. by rotation of the annulus, into and out of registration with the passageways 36. A handle 39 is provided for effecting rotation of the annulus.

Mounted above the feed-board on a cross bar 40 carried on brackets 41 from the side frames, there is a second valve-box 42. The valve-box has a downwardly directed nozzle 43 immediately above the nozzle 16 in the feed-board and of a diameter somewhat less than that nozzle. There is an oscillatory control valve (similar to the valve 55 shown in Figure 6) in the box and a connection through the valve to the nozzle from the suction supply aforesaid. This connection comprises a hollow shaft 44 extending cross-wise of the feed-board from a side bracket 41 to the valve, the shaft constituting both the suction supply pipe and means for transmitting oscillatory motion to the valve. The shaft is arranged for oscillation by the above-mentioned rotatable shaft 21 by means of a cam 46 thereon a rocking lever 47 pivoted to the frame member 12 and of which one end is received within a forked arm 48 on the shaft. There may also be a relief valve 49, similar to that described above, in the valve box.

In the second example (see Figure 6) there are two valve boxes 13, 42, suction nozzles 16, 43 and relief valves 37, 49 as described above. In this example there is in each valve box a piston 30 and cylinder 31 connected between the control valve and the nozzle. The control valve in box 13 is as shown at 17 in Figure 3 and the valve in box 42 comprises an oscillatory member 55 on shaft 44 and having a radial passage 56 communicating at appropriate times with passage 57 leading to orifice 43. Each piston is arranged to operate an electric switch 58, 59 and the two switches are connected in series in an electric control circuit so that it is necessary for both switches to be closed, by movement of the two pistons on closure of both suction orifices, before the control circuit is completed to energise a solenoid 66 to stop the machine. Alternatively the switches may be normally closed and connected in parallel so that it is necessary to open both switches to operate the control circuit. In a further alternative the electric switches are replaced by valves controlling a pneumatic system.

In the operation of each of the above examples after a sheet 65 (Figure has been registered against the front lays 11 and the side lays, the valves are operated to admit suction to both nozzles. If there is only one sheet then only one of the nozzles can be sealed by the sheet and, as the other nozzle is open for ingress of air to the source of suction it is not possible for sufficient suction to build up to operate the piston and cylinder. If, however, there are two sheets (as shown at 65 and 66 in Figure 5) then both nozzles will be sealed, no air can enter and the suction will build up to operate the piston and so to stop the machine.

I claim:

1. A sheet feeding mechanism of the kind embodying a feed-board onto which a succession of single sheets are to be fed characterized by a detector for detecting the inadvertent feeding on to the board of two superposed sheets comprising two opposed suction nozzles separated by slightly more than twice the thickness of one of the sheets and located to receive between them and be sealed one by a single sheet on the board and both by two superposed sheets on the board, a connection to each nozzle from a common source of suction, two suction control valves for the connections to the two nozzles respectively, positioned above and below the feed-board respectively and directly connected to the two nozzles to which they are appropriated, means for operating the valves extending to the valves above and below the feed-board and means responsive to the change in suction resulting from sealing of both nozzles for stopping the operation of the feeding mechanism.

2. A sheet feeding mechanism as claimed in claim 1 in which the responsive means comprise two pistons and cylinders, one between each control valve and its adjacent nozzle respectively, and in which the two pistons and cylinders are operable together to stop the mechanism.

3. A sheet feeding mechanism as claimed in claim 2 in which there is a solenoid operated device for stopping the mechanism, an electric circuit controlling the solenoid and switch means for the circuit operated by the two pistons and cylinders.

4. A sheet feeding mechanism of the kind embodying a feed-board onto which a succession of single sheets are to be fed characterized by a detector for detecting the inadvertent feeding on to the board of two superposed sheets comprising two opposed suction nozzles separated by slightly more than twice the thickness of one of the sheets and located to receive between them and be sealed one by a single sheet or both by two superposed sheets lying on the board, connections to the two nozzles from a cornmon source of suction, two suction control valves for the connections to the two nozzles respectively, positioned above and below the feed-board respectively and directly connected to the two nozzles to which they are appropriated, means for operating the valves extending to the valves above and below the feed-board, whereby when both valves are open the degree of suction which can build up in the connection is greater when both nozzles are sealed respectively by two sheets between the nozzles than it is when only one of the nozzles is sealed by a single sheet between them and the other is open for ingress of air and means responsive to the greater build-up of suction to stop the mechanism.

5. A sheet feeding mechanism as claimed in claim 4 in which there is also provided for the lower nozzle an adjustable relief valve in the suction connection to the nozzle. the relief valve controlling a lead to the atmosphere and being positioned in the connection to the nozzle immediately adjacent tothe control valve.

6. A sheet feeding mechanism as claimed in claim 4 in which the valve in the connection to the lower nozzle comprises a piston and the means for operating the valve comprise a rotatable shaft extending in the cross-wise direction beneath the feed-board.

7. A sheet feeding mechanism as claimed in claim 4 in which the valve in the connection to the upper nozzle comprises an oscillatory valve member and the means for operating the valve comprise an oscillatory shaft operatively connected to the valve member and extending in the cross-wise direction above the feed-board.

8. A sheet feeding mechanism as claimed in claim 4 in which the responsive means aforesaid comprise a piston and cylinder between one of the control valves and the adjacent nozzle which is operable when the suction builds up on closure of both nozzles.

References Cited in the file of this patent UNITED STATES PATENTS 588,452 Leiger Aug. 17, 1897 597,652 McNutt Jan. 18, 1898 624,229 Leiger May 2, 1899 

